Support structure for and method of using plastic Bags

ABSTRACT

A collapsible support frame has a top opening and open sides to allow a plastic bag to be received through the top opening. Anchoring members protrude outwardly from the frame to engage the top of the open bag after it is folded over the frame. The anchoring members are dimensioned to at least partially stretch the folded-over portion of the bag to insure that the bag remains secured to the frame even when the bag is weighed down with materials placed in the bag, such as trash, recyclables, etc. After the bag is full and is to be removed from the frame the folded over portion is manually urged over the anchoring members to separate the bag from the frame. While the bag is held in the frame the exterior surfaces of the bag are visible and preferably bear messages, advertisements, etc.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to Provisional Patent Application No. 61/571,800 filed on Jul. 6, 2011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to a system for and method of recycling and re-using plastic bags and, more specifically, to a support structure for and method of re-using supermarket-type plastic bags as trash or garbage bags.

2. Description of the Prior Art

Plastic shopping bags are among the most widely used consumer items on Earth. Their light weight, low cost, and water resistance make them convenient for carrying groceries, clothing, and other routine purchases. Weighing just a few grams and averaging a few millimeters in thickness, plastic bags might seem thoroughly innocuous—were it not for the sheer number produced. Factories around the world churned out 4-5 trillion of them in 2002, ranging from large trash bags to thick shopping totes to flimsy grocery sacks.

Compared with paper bags, producing plastic ones uses less energy and water and generates less air pollution and solid waste. Plastic bags also take up less space in a landfill. But many of these bags never make it to landfills; instead, they go airborne after they are discarded—getting caught in fences, trees, and clogging gutters, sewers, and waterways.

The first plastic “baggies” for bread, sandwiches, fruits, and vegetables were introduced in the United States in 1957. Plastic trash bags started appearing in homes and along curbsides around the world by the late 1960s. North America and Western Europe account for nearly 80 percent of plastic bag use—though the bags are increasingly common in developing countries as well. Each year, Americans throw away some 100 billion polyethylene plastic bags. (Only 0.6 percent of plastic bags are recycled.) In January 2002, the South African government required manufacturers to make plastic bags more durable and more expensive to discourage their disposal—prompting a 90-percent reduction in use. Ireland instituted a charge-per-bag tax in March 2002, which led to a 95-percent reduction in use. In the early 1990s, citizens groups led a successful campaign to ban plastic bags. Australia, Canada, New Zealand, the Philippines, Taiwan, and the United Kingdom also have plans to ban or tax plastic bags.

Supermarkets around the world are voluntarily encouraging shoppers to forgo plastic bags—or to bring their own bags—by offering a small per-bag refund or charging extra for plastic.

Some manufacturers have introduced biodegradable or compostable plastic bags made from starches, polymers or poly-lactic acid, and no polyethylene—though these remain prohibitively expensive and account for less than 1 percent of the market.

The organizers of the 2000 Olympic Games in Sydney, Australia, were able to collect 76 percent of the food waste generated at the sports venues and athletes' village by using biodegradable utensils and plastic bags that composted as easily as the food and eliminated the need to separate the plastic.

The problems associated with plastic bags continue to be overwhelming. Because plastic bags are perceived as being very low lost and disposable little serious thought has been given to reusing plastic bags to decrease the overall utilization of such bags.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to eliminate some of the problems associated with plastic bags.

It is another object of the invention to provide a plastic shopping bag support frame designed to at least double the utilization of plastic shopping bags that can initially be used by retail establishments for packing or bagging products, such as groceries, and subsequently be reused by consumers to dispose of or recycle trash or garbage in lieu of using conventional or traditional single-use garbage and recycling bags to dispose trash.

It is still another object of the invention to provide a plastic bag support frame as in the previous object that is simple in construction and economical to manufacture.

It is yet another object of the invention to provide a plastic bag support frame of the type under discussion that exposes imprinted indicia, such as company logos and advertising, on the outside surface of plastic bags to subsidize the cost of the bag supports frame and/or associated specific size bags to be used with the bag support frame.

Is a further object of the invention to provide a plastic bag support frame as in the previous objects that is collapsible when shipped and stored.

It is still a further object of the invention to provide a plastic bag support frame of the type under discussion that is simple and convenient to use.

It is yet a further object of the invention to provide a plastic bag support frame as in the previous objects that promotes multiple uses of plastic-type shopping bags used by retail establishments for packing or bagging products.

It is an additional object of the invention to provide a plastic bag support frame that promotes the ecology by enabling multiple uses of plastic bags by subsidizing the plastic bags and support frame at least partially by advertising revenues.

In order to achieve the above objects, as well as others that will become evident hereinafter, the present invention relates to a support structure for recycling by re-using plastic bags of the type frequently used in supermarkets for packing or “bagging” groceries and other items sold in supermarkets, and a method for using the support structure. The support structure is intended to be used for supporting a plastic bag generally defining a bag axis and open end. The support structure includes a frame that generally defines an interior volume or space and an upper frame opening arranged in a generally horizontal plane when the support structure is supported on a horizontal surface. The upper frame opening defines a perimeter “P” substantially corresponding to a perimeter “p” of a bag to be supported within the interior volume or space of the support frame. Protuberance means is provided on said frame proximate said upper frame opening, said protuberance means being dimensioned to engage and retain an open end of a bag within said support frame with said open end of the bag stretched and pulled over said protuberance means.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof with reference to the annexed drawings wherein:

FIG. 1 is a perspective view of a plastic bag support frame for supporting a plastic bag and exposing imprinted indicia on outside surface of the plastic bag in accordance with the present invention;

FIG. 2 is a fragmented side elevational view of a leg frame member on one side of the plastic bag support frame shown in FIG. 1;

FIG. 3 is a fragmented right end elevational view of the leg frame member shown in FIG. 2;

FIG. 4 is a fragmented left end elevational view of the leg frame member shown in FIG. 2;

FIG. 5 is a fragmented side elevational view of a leg frame member on the other or opposing side of the plastic bag support frame shown in FIG. 1;

FIG. 6 is fragmented a right end elevational view of the leg frame member shown in FIG. 5;

FIG. 7 is a fragmented left end elevational fragmented view of the leg frame member shown in FIG. 5;

FIG. 8 is a top plan view of the leg frame member shown in FIG. 5;

FIG. 9 is a bottom plan view of the leg frame member shown in FIG. 5;

FIG. 10 is a side elevational view of the leg frame member shown in FIG. 1;

FIG. 11 is a left end elevational view of the leg frame member shown in FIG. 5;

FIGS. 11 a-11 c are cross-sectional views of the leg frame member shown in FIG. 11 respectively taken along lines G-G, H-H and I-I;

FIG. 12 is a front side elevational view of an interior surface of a connecting member of the bag support frame of FIG. 1;

FIG. 12 a is a cross sectional view taken along line F-F in FIG. 12;

FIG. 13 is a rear side elevational view of an exterior surface of the connecting member of FIG. 12;

FIG. 14 is a perspective view similar to FIG. 1 but showing the bag support frame in the process of being collapsed or expanded;

FIG. 15 is similar to FIG. 1 but with the leg frame members in the fully expanded position and supporting a plastic bag the exterior surface of which bears indicia printed thereon that is exposed through the bag support frame;

FIG. 16 is a perspective view of another embodiment of the invention in the form of a non-collapsible bin or basket;

FIG. 17 is a top plan view of the bin or basket shown in FIG. 16; and

FIG. 18 is a cross-sectional view of a corner of the bin or basket shown in FIG. 17 taken along line 18-18.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now more specifically to the Figures, in which identical or similar parts are designated by the same reference numerals throughout, and first referring to FIG. 1 a plastic bag support frame for supporting a plastic bag and exposing imprinted indicia on an outside surface of the bag is generally designated by the reference numeral 10.

The support frame 10 is substantially formed of four components or elements the first of which is a leg frame member 12. Another leg frame member 14 is spaced from the leg frame member 12, both leg frame members defining generally vertical parallel planes when the bag support frame 10 is in its fully expanded position as shown in FIG. 1.

Generally parallel connecting members 16, 18 are arranged in a common horizontal plane “P” (FIG. 1) during use of the device when the frame is in its upright or expanded position suitable for receiving a plastic bag. The leg frame members and connecting members are pivotally connected to each other, as will be more fully explained.

Referring to FIGS. 1 and 2 the leg frame member 12 is formed of two spaced parallel vertical legs 12 a, 12 b bridged by a cross-member 12 c rendering the leg frame member 12 suitably rigid and preferably of unitary construction. Similarly, the leg frame member 14 is formed of two spaced parallel vertical legs 14 a, 14 b that are connected to each other by means of an integrally formed cross-member 14 c. The leg frame members 12, 14 are preferably identical in construction to facilitate manufacturing, assembly, shipping and storage.

The legs 12 a, 14 b have offsets 14 h (FIGS. 2, 5 and 10) so that the associated legs 12 b and 14 a are capable of collapsing into a plane substantially coextensive or proximate to the plane P extending across the top of the bag frame 10 in the fully expanded position, as shown in FIG. 1. The top of the bag frame 10 is formed of the connecting members 12 c, 14 c, 16 and 18 that together form a generally horizontal support frame 20. The offsets 12 h, 14 h inwardly offset the legs 12 a and 14 b to accommodate the respective legs 14 a and 12 b when the frame leg frame members 12, 14 are collapsed inwardly, as suggested in FIG. 14, into the common plane P (FIG. 1). By placing the offsets 12 h, 14 h on diagonally opposite corners the bag frame, the leg frame members 12, 14 can be identical in construction thus reducing manufacturing costs and facilitating assembly.

Since the leg frame members 12, 14 have identical constructions only one leg frame member 14 will be described, it being clear that the same structural features described for leg frame member 14 will apply equally to leg frame member 12. Thus, referring to FIGS. 5-11 c the leg frame member 14 includes integrally formed legs 14 a, 14 b and cross-member 14 c. Leg 14 b is inwardly offset by means of offset 14 h to accommodate leg 12 b as described above. The leg frame members 12, 14 can be formed of any material, such as die-cut sheet metal or molded plastic. In either case, the thickness of the walls can be as low as 1/16″. To strengthen the members and render them more rigid they are preferably provided with angled wall portions (or other known stiffening devices such as ribs) 14 d on the legs 14 a, 14 b all of which extend inwardly in the direction of the opposing leg frame member 12. These additional wall portions serve to strengthen the parts to make them more rigid.

Each of the legs 14 a, 14 b is provided with holes 14 f for securing the leg frame members to the connecting members 16, 18 and with openings or holes 14 g that form part of a detent locking mechanism for locking the legs in the fully open conditions shown in FIG. 1.

Referring to FIGS. 12 and 13 the details of the connecting member 16 is shown, the same description applying equally to the connecting member 18. Again, to reduce manufacturing costs, the connecting members 16, 18 are preferably identical. The connecting member 16 is provided with an inwardly directed wall portion 16 f to render the part stronger and more rigid as described in connection with the leg frame members 12, 14. The length “L” (FIG. 15) of the connecting members 16, 18 can be selected to be any desired length. However, in the embodiment described the length L is equal to 14″. Likewise, the length of the cross-members 12 c, 14 c can be any desired length but in the embodiment described the dimension is selected to be 8″.

An important feature of the invention is that the connecting members 16, 18 are provided with extensions or protuberances 16 a, 16 b and 18 a, 18 b, respectively. These extensions include generally downwardly directed edges 16 c that extend a predetermined distance beyond the length L of the connecting members, such extensions “s” project approximately 0.6″ from the outer edge T of the rim and extend inwardly at 16 f to a position 16 f that substantially passes through the ends of the flat portions of the connecting members. In this way, the distances between the innermost edges of the inwardly directed portions 16 f are all so spaced from each other a distance approximately equal to L. The inwardly directed portions 16 f serve as gripping portions for a plastic bag inserted within the bag frame member as will be more fully described in connection with FIG. 15. The specific nature of the bag gripping portions is not critical and any protuberances extending beyond the perimeter p of the horizontal support frame or other gripping mechanisms may be used with different degrees of advantage. Although the extensions or protuberances project approximately 0.6″ outwardly from the rim T of the upper opening the dimension “s” can be within the range of 0.25″-0.75″. Reducing “s” below this range may compromise the holding power on the bag while increasing it above this range can damage or puncture the bag. The optimum dimension will also be a function of the thickness and stretchability of the material from which the bag is made.

The connecting members 16, 18 are provided with holes 16 d at opposite ends dimensioned and arranged to cooperate with holes 12 f, 14 f on the legs frame members and the holes are aligned with each other so that any suitable fastener, such as a rivet, screw and bolt, etc. can extend through the holes and serve as pivot points about which the leg frame members can pivot relative to the stationary connecting members 16, 18.

The connecting members 16, 18 are also provided with inwardly directed indentations 16 e, 18 e that serve as detents that can be resiliently and selectively received or removed from the holes 12 g, 14 g in the associated legs frame members. Thus, when the leg frame members are moved to the open operative positions as shown in FIG. 1 the indentations 16 e, 18 e are received and snap into the associated holes 12 g, 14 g to maintain the leg frame members in the open or expanded position as shown in FIG. 1. However, when it is desired to collapse the unit manual rotation of the leg frame members 12, 14 inwardly, as suggested in FIG. 14, withdraws the indentations 16 e, 18 e from the associated holes 12 g, 14 g in the legs frame members due to temporary deformations or movements of the relative members to overcome the interference fits when the retaining forces are manually overcome by forcibly pivoting the leg frame members relative to the connecting members. The indentations 16 e, 18 e can also be replaced by spring loaded or biased bearings as is well known to those skilled in the art, or any other detent arrangements can be used to maintain the leg frame members in the open positions shown in FIG. 1 until urged by a user by application of a manual force sufficient to overcome the biasing forces of the detent mechanisms used.

Referring to FIG. 15, the lower ends of the legs define a base and a support plane coextensive with the surface on which the bag frame 10 is supported. This support plane is generally a horizontal plane, such as a floor of a living enclosure. The cross-members 12 c, 14 c and the connecting members 16, 18 also define an opening in the plane P that is spaced from and substantially parallel to the support plane at the base. In the embodiment described, the upper plane P of the opening is likewise arranged in a horizontal plane. The lengths 1 of the connecting members in the widths w of the cross-members together define a perimeter p=2L+2w.

The height “H” the bag frame member is not critical and any desired height may be used. In the embodiment described, the height H is 14″. A feature of the invention is that the plastic bag 30 defines a perimeter “p′” that is substantially equal to the perimeter p of the opening of the bag frame and has a height “H” extending from the opening of the bag to the bottom of the bag that can be equal to, less than or greater than the height H. The exterior surface of the bag is preferably imprinted with a logo or advertising 40 so that when the bag 30 is inserted into the bag frame as shown on FIG. 15 the logo and/or the advertisement 40 will be exposed and visible.

In use, the bag frame 10 is initially shipped and provided to a consumer in a collapsed state with the leg frame members fully inwardly pivoted. When the bag frame is ready to be used the leg frame members 12, 14 are pivoted about rivets 24 or other fasteners, to the positions shown in FIGS. 1 and 15. At this point, the detent mechanism 12 g, 14 g and 16 e, 18 e snap the components together and the frame members remain in the open or expanded position. A plastic bag 30, a bag commonly referred to as a “T-Shirt Bag” is the best style of bag to use, and it can now be inserted through the opening at the top of the bag support frame member until the bottom of the bag reaches the floor or other support surface. The opening of the bag is then folded over each of the upper edges of the bag frame a distance Δh (FIG. 15) to cover the cross-members 12 c, 14 c and connecting members 16,18, the four elongate members 12 c, 14 c, 16 and 18 together forming a substantially horizontal support frame 20. However, importantly, when the opening of the bag is folded over the support frame 20 the bag 30 is preferably at least partially stretched over the outwardly projecting extensions or protuberances 16 a, 18 a, 16 b, 18 b. Due to the elasticity of the plastic bags the stretched portions of the bag tends to revert to their initial unstretched state and so the opening of the bag, once stretched, closes in on and attaches to the lower portion of the protuberances located at 16 f′, 18 f′. Such stretching of the bag and engagement with the protuberances 16 a, 18 a, 16 b, 18 b. ensures that the top or opening of the bag remains engaged with the bag frame and does not inadvertently disengage from the bag frame to collapse and fall through the opening but remains in the position shown on FIG. 15 to facilitate the use of the bag for depositing trash. Once the bag 30 is full the upper part of the bag that had been stretched over the protuberances 16 a, 18 a, 16 b, 18 b then the engaged part of the bag is again stretched and forcibly pulled over the upper support frame 20 so that the bag may be removed from the bag support frame 10.

As mentioned above T-shirt bags are best suited for use for stretching the bags over the protuberances 16 a, 18 a, 16 b, 18 b. T-Shirt bags are called “T-Shirt” because they look like a sleeveless T-Shirts. T-Shirt bags are plastic shopping bags that have handles extending from the body of the bags and are the most commonly used plastic supermarket bags. T-Shirt bags are best suited for use because during the manufacture of these bags they are die cut to form handles for the bags. When placing these bags over the top frame virtually all T-Shirt bags form relatively loose pockets of material that are located where the bag's handles attach to the bag. These loose pockets of material then line up with the protuberances 16 a, 18 a, 16 b, 18 b. When mounting a T-Shirt bag, the opening of the bag is stretched over these protuberances 16 a, 18 a, 16 b, 18 b, while the protuberances themselves comfortably project into the above mentioned loose pockets of material located on the T-Shirt bag. Because the opening of the bag is stretched over the protuberances, the opening of the bag then catches onto the bottom part of the protuberances located at 16 f′, thus securely anchoring the bag into position, until the opening of the bag is once again stretched over the protuberances and taken off the frame. Also, most T-Shirt bags distributed in supermarkets and stores come in standard sizes where the opening of the bag is of a specific perimeter dimension. This means that the size and spacing of the horizontal support frame 20 and the protuberances 16 a, 18 a, 16 b, 18 b can be specifically designed for the most commonly used sizes of T-Shirt bags.

The bags 30 are preferably dimensioned to be frame specific. Thus, if the bottoms of the bags are to rest or contact the floor or support surface the height of the bag needs to be h′≈(H+Δh). However, as should be clear, if h′>H+Δh more of the bag can be rolled over the horizontal support frame 20 and when h′<H+Δh the bottom of the bag may not reach the floor or support surface but remain suspended to hang on the bag support frame during use.

It will be evident that the bag frame 10 in accordance with the present invention is extremely simple construction and economical to manufacture. However, another embodiment is shown in FIGS. 16-18 where the invention is incorporated into a more conventional looking, non-collapsible container or bin 10′. The bin 10′ may be made of metal, plastic or hard rubber or any other rigid material. Bins of this type are typically tapered so that they can be stacked during storage or shipment the specific shape of the bin for purposes of the invention is not critical and is shown to have an upper opening with a length “L” and a width “w”, and a height “H”. While the perimeter at the upper opening is approximately P=2L+2w the actual perimeter is somewhat less because of the rounded or curved corners “c”. In one example of a typical bin, the bin opening is about 13×9.2 inches, but its perimeter is not 44.4 inches because of the rounded corners c. While generally rectangular its shape also somewhat resembles an oval that is 13 inches long by 9.2 inches wide. Actual measurement of the perimeter P indicated that the perimeter P of the bin was approximately 41 inches instead of the 44.4 inches had the corners c not been rounded out—an almost 8% reduction in the perimeter. Measurements of the perimeters “p” of the opening of typical “supermarket” type plastic bags of “best fit” bags indicated the range of perimeters “p” of the plastic bags from loose bags to tight bags that work with the bin 10′. It was determined that:

a) best fit—40 inch perimeter or a perimeter 2.5% smaller than the bin perimeter P.

b) loose fit—41 inch perimeter or a perimeter equal to the bin perimeter P.

c) tight fit—39 inch perimeter or a perimeter 5% smaller than the bin perimeter P.

Therefore, the range of perimeters of plastic bags that will work with a bin of perimeter P can be defined thus:

0.95P<p≦P.

This allows almost any but preferably frame-specific bags, that are “T-Shirt” bags with handles of the type used by retail establishments to bag products, such as supermarkets bags for packing groceries, can be initially used for bagging products for carrying the products home from the store and then re-used for throwing away and recycling trash. Preferably, the bags 30 are dimensioned and of the type (T-Shirt bags) as suggested above, although almost any bags can be used with the bag frame 10 or trash bin 10′, with different degrees of advantage. The use and reuse of the bags will reduce the number of bags that are used by allowing users to use the bags for transporting products and also for removing trash, whereas currently consumers frequently discard the bags provided by the retail establishments and purchase “plastic garbage bags” that are only used once for that specific purpose. The plastic bags 30 are preferably, but not necessarily, made of a biodegradable material to further promote a green environment.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments for carrying out this invention, but that the invention will include all embodiments falling within the scope of the invention. 

1. A support structure for supporting a thin walled stretchable plastic bag generally defining and axis and an open end, the support structure comprising a frame generally defining an interior volume or space and an upper frame opening arranged in a generally horizontal plane when the support structure is supported on a horizontal surface, said upper frame opening defining a perimeter P substantially corresponding to a perimeter p of an opening of a plastic bag to be supported, and protuberance means on said frame proximate to said frame opening, said protuberance means being arranged and dimensioned to engage and retain an open end of a bag placed within said interior volume with said open end stretched and pulled over said protuberance means.
 2. A support structure as defined in claim 1, wherein said frame is formed of a plurality of frame members linked to each other and collapsible for storage.
 3. A support structure as defined in claim 1, wherein said frame member is a non-collapsible bin.
 4. A support structure as defined in claim 1, wherein perimeters p of plastic bags for use with a bin of perimeter P is selected to be within the range 0.95P<p≦P.
 5. A support structure as defined in claim 4, wherein p˜0.975P
 6. A support structure as defined in claim 1, wherein said protuberance means comprises at least one protuberance that projects in a direction away from said upper frame opening to effectively increase the perimeter P.
 7. A support structure as defined in claim 6, wherein a plurality of protuberances are provided distributed about said upper frame opening.
 8. A support structure as defined in claim 7, wherein said upper frame opening is generally rectangular and one protuberance is provided at each corner of said frame opening.
 9. A support structure as defined in claim 6, wherein said protuberances have rounded ends to prevent said protuberances from puncturing the plastic bag when stretched over said protuberances.
 10. A support structure as defined in claim 6, wherein said protuberances have a dimension extending beyond said upper frame opening that is at least P.
 11. A support structure as defined in claim 6, wherein said protuberances are arranged about said upper frame opening to generally be aligned with pockets or recesses to each side of handles of plastic bags.
 12. In combination of a thin walled stretchable plastic bag and a support structure for supporting said thin walled stretchable plastic bag, said bag generally defining and axis and an open end, said support structure comprising a frame generally defining an interior volume or space and an upper frame opening arranged in a generally horizontal plane when the support structure is supported on a horizontal surface, said upper frame opening defining a perimeter P substantially corresponding to a perimeter p of an opening of a plastic bag to be supported, and protuberance means on said frame proximate to said frame opening, said protuberance means being arranged and dimensioned to engage and retain an open end of a bag placed within said interior volume with said open end stretched and pulled over said protuberance means.
 13. A support structure as defined in claim 6, wherein said bag comprises a T-shirt type bag.
 14. A support structure as defined in claim 6, wherein P is equal to approximately 41″ and said bag has a perimeter within the range of 39-41″.
 15. A support structure as defined in claim 6, wherein P is equal to approximately 41″ and said bag has a perimeter p=40″.
 16. A support structure as defined in claim 12, wherein perimeters p of plastic bags for use with a bin of perimeter P is selected to be within the range
 0. 95P<p≦P.
 17. A support structure as defined in claim 16, wherein p˜0.975P.
 18. A method for securing a thin walled stretchable plastic bag generally defining and axis and an open end to a support structure comprising the steps of providing a support structure comprising a frame generally defining an interior volume or space and an upper frame opening arranged in a generally horizontal plane when the support structure is supported on a horizontal surface, said upper frame opening defining a perimeter P substantially corresponding to a perimeter p of an opening of a plastic bag to be supported, and protuberance means on said frame proximate to said frame opening, said protuberance means being arranged and dimensioned to engage and retain an open end of a bag placed within said interior volume with said open end; stretching the open end of the bag to enlarge the perimeter of the open end beyond the value p; pulling said stretched bag open end over said protuberance means; and releasing the bag open end to restore the perimeter of the bag open end to bring at least portions of the bag into interference engagement with said protuberance means to secure the bag open end to said upper frame opening.
 19. A method as defined in claim 18, wherein a plurality of protuberances are provided distributed about said upper frame opening and the stretched bag open end is pulled over and engaged with each of said protuberances.
 20. A method as defined in claim 12, wherein perimeters p of plastic bags for use with a bin of perimeter P is selected to be within the range 